By using isolated and purified populations of mouse gastric parietal cells and enriched fractions of mucous or chief cells, studies on the functional role of these cells as correlated to their ultrastructure will be undertaken. This proposed research will utilize our recently adapted technique of gastric epithelial cell dissociation with pronase and fractionation of these cells into different populations according to their size by velocity sedimentation. These isolated cells are viable for some time and maintain some of their normal activities. The structure of these isolated cells will be studied by phase contrast, interference contrast, scanning electron microscopy, and transmission electron microscopy. Freeze etch and freeze fracture studies will be emphasized. Along with physiological measurements of secretory activity and respiration, the effects of stimulation or inhibition of activity will be monitored and the ultrastructure of the cells compared. We anticipate that this approach will provide us with a more definite and, hopefully, conclusive evidence for the functional role and structure of some of the various cell types in this complex organ. Initially, the relatively simple separation of the parietal cells which are more than 20 mu in diameter in contrast to the other cell types which are less than 15 mu in diameter will be used for most of our studies. A specific project with parietal cells is to determine if they can transport chloride ions in a unidirectional manner, and if so, use this data as an index of gastric acid secretion. The secretions of fractions rich in mucous cells or chief cells will be compared with parietal cells in their secretory activity. Some biochemical determination of parietal and mucous cell composition is also contemplated for the normal, stimulated and inhibited parietal cells.